The present invention relates to producing a look and feel of prewashed denim using a simplified process and technique.
The current system of producing xe2x80x9cprewashedxe2x80x9d denim materials, e.g., denim jeans, washes the jeans in a chemical environment that simulates a number of washings.
Denim jeans are typically washed 100 pairs at a time in a 500 pound plus washing machine. The washing is typically carried out for two hours, with specific concentrations of desizing agents, enzymes and softening agents.
The purposes of the wash include: 1) Remove the waxy xe2x80x9csizingxe2x80x9d from the denim, 2) Remove part of the indigo dye, 3) Soften the rigid denim, 4) Produce a stonewashed type look and 5) Provide the unique seam abrasion (worn xe2x80x9cladder typexe2x80x9d look) on all the seams on the jeans.
Stones can be used to replace some or all of the enzymes for purposes of removing some of the color in the denim during the wash process and to provide the seam abrasion. In some cases the wash water has to be drained and filled three times. It is not unusual to use 35 gallons of water per pair of jeans washed.
The enzyme washing process has numerous drawbacks. It is reported that the true total cost for enzyme washing one pair of denim jeans is about $3 per pair when all unit cost and freight parameters are considered. The enzyme washing process also significanty reduces, by, for example, as much as 36%, the tensile and tear properties of the denim. The enzyme washing process also produces numerous defects such as back pocket blowout that results in scrap or rework. Also, as described above, the enzyme washing process uses as much as 35 gallons of water per pair of jeans. There are also other significant environmental problems associated with the handling and disposal of the enzymes and waste water.
U.S. Pat. No. 5,567,207, assigned to Icon, Inc, disclosed a water free method for color fading textile materials with the use of a laser. The patent specifically indicated that the wavelength of the laser should be chosen such that it is strongly absorbed by the dye, but not by the textile material. Icon used a Yag Laser for this purpose with a wavelength of 1,064 nanometers.
Accordingly, the Icon patent taught that the Yag laser process will provide optimum dye photo-decomposition, and also specifically that the material should not be damaged by the laser exposure. The Icon patent did not teach a specific method to laser-scribe a pair of denim jeans to achieve the specific color, cast and character that is obtained from an enzyme or stone wash.
In contrast, previous applications by the assignee of the present invention have described laser scribing rigid denim by intentionally damaging the material. This is done by scanning the laser across the denim. However, previous attempts, while they may do an effective job of removing the indigo dye, simply cannot replicate the unique cast and character of denim obtained from enzyme or stonewashing. Our previous applications have described using a CO2 laser with a wavelength an order of magnitude higher than the Yag laser in order to remove the dye and alter the surface chemistry. Also, only specific and unique laser processes must be used other than the conventional scanning the laser across the denim material in an edge-to-edge or dot-to-dot method. The wavelength of the. CO2 laser is 10,600 nanometers. This characteristic does alter the surface chemistry)of the fabric upon lazing, such that the fabric is indeed damaged, albeit at an acceptable level.
For example, TechnoLines, Inc. has determined that the percent reduction in warp tensile strength from a CO2 lazing process which replicates the unique pattern and look of stonewashed or enzyme washed denim is about 10%. This is, however, acceptable, given that the conventional enzyme washing process reduces warp tensile properties by about 36%. Therefore, the TechnoLines, Inc. laser scribing process alters the surface chemistry and removes the indigo dye and clearly but acceptably damages the textile material and produces the denim enzyme washed look as disclosedin this specification.
The inventors recognized a critical need to develop a process to reduce the exposure of the denim to the harmful enzymes and thus reduce the water and chemical requirements associated with the enzyme washing process. The inventors also recognized a critical need to develop a process to eliminate the laundry process as it exists today and achieve product performance, manufacturing cost, environmental and turnaround time benefits.
The present disclosure teaches some form of washing must be used to eliminate the residue on the denim sheet after laser scribing. One such process disclosed by this disclosure is an on-line washing process where the denim ribbon is lazed and then passed through feed rollers and a bath to wash and rinse the residue, including the sizing material from the denim material. While washing is still necessary, that washing is much shorter than previously necessary, and also can be done on line as part of the manufacturing process.
Another irmportant issue is seam abrasion. The Icon patent does not teach any methodology to provide the unique seam abrasion on denim which is obtained from the enzyme washing process. In order to eliminate the enzyme washing process, a new technology is disclosed that provides the worn xe2x80x9cladder typexe2x80x9d look along the seams that is obtained from the enzyme washing process. The present disclosure describes two techniques to provide seam abrasion without the use of the enzyme washingxe2x80x94a first using rocks in the washer without enzymes, and a second using lasers.
Best results are obtained by lasing while staying within a specific EDPUT range (energy density per unit time).